Battery venting system

ABSTRACT

A battery venting system that is useful for cordless power tools. The system can include a cell that may have a sleeve with a plurality of apertures surrounding a peripheral side face of the cell to enhance heat dissipation from the cell. A plurality of cells may be electrically connected to form a cell pack. A carrier includes an upper carrier and a lower carrier to sandwich a plurality of cells that are aligned parallel to each other. The carriers include at least one vent hole that are aligned with a gap formed from adjacent cells to define an elongated fluid flow path. A charger may be provided to receive a housing containing the carrier and may be provided with a fan to direct a flow into the fluid flow path.

BACKGROUND OF THE INVENTION

The present invention relates generally to a battery venting system thatis useful for cordless power tools. The system includes one or more ofbattery cells, sleeves that may surround the battery cell, a carrierthat can position and hold a number of battery cells to form a cellpack, and a charger useful with the battery cells and/or carrier.

Rechargeable nickel-cadmium cells and nickel-metal hydride cells arewidely used as a battery power source for portable apparatus, such aspower tools. Typically, nickel-cadmium cells or nickel-metal hydridecells are used in the form of a cylindrical cell that has a cylindricalshape. In the portable apparatus, the cylindrical cells are used aloneor more typically in the form of a cell pack in which a plurality ofcells are connected and are contained within a housing that can beremovably attached to an apparatus.

FIG. 1 shows a typical cylindrical cell, which has a cylindrical case 1that contains the cell materials in a closed fashion by a cover 11. Aconductive projection 11 a is formed in the cover 11, and a safety valvefor releasing gasses is disposed in the projection 11 a. Generally, thecover 11 having the projection 11 a the positive electrode and the case12 is the negative electrode. A sleeve 13 usually surrounds theperipheral side of the cell and is formed from an electricallyinsulating material so that when the battery cells are intentionally orunintentionally touching each other at the peripheral side face, thebattery cells will not short out or discharge.

When the cylindrical cell 1 is to be used as a power source for anapparatus, a plurality of cells are connected to each other to form acell pack, as shown in FIG. 2. Adjacent cells 1 are bridged by anelectrically conductive plate 9, such as a nickel plate. The plate maybe attached by spot-welding or other methods of attaching to theprojection 11 a of the cover 11 of one of the cells and the bottom faceof the case 12 of the other cell, respectively. To further secure andposition the plurality of cells, it is known to wrap the periphery ofthe outermost cells with a shrinkable plastic or tape.

A disadvantage to providing an electrically insulating case around eachcell is that when a plurality of cells are provided to form a cell pack,heat generated upon discharge and upon recharging operations is noteasily dissipated. Likewise, when a cell pack is wrapped with shrinkableplastic or tape, the generated heat is further hindered fromdissipation. When the temperature of the cell is raised as a result ofthe heat generation, self-discharge may reduce the cell capacity orshorten the service life of the cell. This problem is also applicable tosealed-type cells or other types such as rectangular cells.

Accordingly, there have been attempts to address this issue by providingcell holders such as that shown in U.S. Pat. No. 5,578,392, particularlyFIG. 13. There, a cell holder is provided to hold and positionindividual battery cells. In this cell holder, an upper and a lowerplate is provided to respectively receive the upper and lower portion ofthe individual cells. Each plate has a plurality of spaced apart cellholes into which a portion of the upper or lower portion of a batterycell can be received. Accordingly, a gap is formed between adjacentcells to facilitate heat dissipation during discharge and chargingoperations. Although this solution may be useful, the plates take upspace within the battery pack housing and by virtue of their size stillhinder heat dissipation.

BRIEF SUMMARY OF THE INVENTION

With the above in mind, in one aspect of the present invention, abattery cell having a first terminal and a second terminal is providedwithout an outer case or covering. In one embodiment, the battery cellmay be cylindrically shaped with a first end having a first terminal anda second end spaced from the first end and having a second terminal. Alongitudinal axis extends from the first end to the second end. Aperipheral side face is disposed between the first end and the secondend.

In another aspect of the present invention, a battery cell is providedwith a sleeve to surround the peripheral side face of the cell. Thesleeve is formed from an electrically insulating material and has aplurality of apertures. The sleeve may be formed form paper, plastic, orany other suitable electrical insulating material. The sleeve may alsobe formed of a plastic mesh such as a molded plastic mesh.

The apertures may have a variety of suitable shapes such that theperipheral side face of the cell is sufficiently exposed to allow heatto dissipate while still allowing the cell to be insulated whencontacted by a similar cell having a sleeve. Suitable aperture shapesinclude those selected from a circle, ellipse, parabola, crescent,obround, disc, triangle, rectangle, polygon, and mixtures thereof. Wherethe aperture has a shape that provides a longer side (or a pair oflonger sides) and a short side (or a pair of shorter sides, like anobround, the longer side(s) may be arranged to be parallel to thelongitudinal axis. Alternatively, the longer side(s) may be arranged tobe normal to the longitudinal axis.

In yet another aspect of the present invention, a carrier of a pluralityof battery cells is provided to arrange and hold the plurality ofbattery cells to define a cell pack. The carrier may be used withbattery cells without an outer case, with battery cells having an outercase, or with battery cells having electrically non-conductive sleevesaccording to the present invention. In one embodiment, the carriercauses the terminals on each end of the cells to be positioned in asubstantially same plane.

In this cell pack, a plurality of cells are arranged side-by-side andare generally parallel to their longitudinal axis. An electricallyconductive connecting member connects the cells with each other. Theelectrically conductive material may be configured of a flexiblematerial. Even when vibration or shock is applied to the cell pack,therefore, the force acting between the cylindrical cells is absorbed bythe flexible material of the connecting member.

It is a still further object of the invention to provide a cell carrierin which upper and lower end portions of sealed-type cells are held by arespective upper carrier and lower carrier to define a vent spacebetween adjacent battery cells, thereby allowing heat generated from thesealed-type cells to be dissipated to the exterior via the vent hole.The upper carrier and lower cell carrier are provided with aperturesthat are aligned with the vent space to define an elongated fluid flowpath to allow heat to be dissipated. The upper carrier and lower carrierare also provided with a connecting member receiving area.

According to the present invention, a plurality of battery cells areheld between the pair of upper and lower carriers and heat generatedfrom the cells can be dissipated via the elongated fluid flow path.Since the outward-directed peripheral side faces of the battery cellsmay be free of electrically insulating material and are exposed to theexterior between the pair of upper and lower carriers, heat can also bedissipated from the peripheral side faces of each battery cell.Alternatively, if a sleeve according to the present invention isprovided, i.e., with a plurality of apertures, a substantial portion theperipheral side faces of the battery cells will be exposed to theexterior between the pair of upper and lower carriers so that heat canbe dissipated from the peripheral side faces of each battery cell.

The venting effect can be further enhanced by forcing a fluid such asair past and through the cell pack. For example, in another aspect ofthe present invention, a charger is provided with a fan to force a fluidinto the cell pack where it can pass through adjacent cells.Advantageously, the charger may be configured to provide charging ofmore than a single cell pack, either sequentially or simultaneously. Thecharger is provided with a mechanism to simultaneously force fluid intotwo separate cell, while charging.

The cell pack may be provided with contacts that operatively associatedwith the cell pack to act as a conduit to transfer electricity to themotor of a power tool or to receive a charge from a charger. Inaddition, the cell pack may be provided with an outer casing or housing,typically formed of plastic to define a battery pack.

Additional aspects, objects, and advantages of the invention will becomeapparent from the detailed description, the appended claims, andaccompanying drawings, as well as by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate an embodiment of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings, the same reference numerals indicate thesame parts.

FIG. 1 is a perspective view of a prior art cylindrical battery cell.

FIG. 2 is a perspective view of a plurality of cylindrical battery cellselectrically connected to define a cell pack.

FIG. 3 is a perspective view of a plurality of cylindrical battery cellshaving sleeves according to the present invention and being electricallyconnected to define a cell pack.

FIG. 4 is a perspective exploded view of a carrier for a plurality ofcylindrical battery cells electrically connected to define a cell pack.

FIG. 5 is a perspective view of a carrier for a plurality of cylindricalbattery cells electrically connected to define a cell pack.

FIG. 6 is a perspective view of a battery charger useful forsimultaneously charging two batteries and containing a venting systemaccording to one aspect of the present invention.

FIG. 7 is a rear cut-away view of the charger with elements removed tobetter illustrate the venting system of the present invention. Oneembodiment of the duct that forms a portion of the venting system isshown with a portion removed to better illustrate the flow of fluidthrough the duct and to a battery pack that houses the carrier of thepresent invention. A portion of the battery pack housings are cut-awayto show the carrier. In addition, the battery pack housings are is shownjust before engagement with the charger.

FIG. 8 is a bottom view of a portion of a venting system for a batterycharger according to one aspect of the present invention.

FIG. 9 is a bottom view of one embodiment of a duct that forms a portionof the venting system useful in a battery charger that is capable ofreceiving two battery packs.

FIG. 10 is a bottom view of a battery charger that is capable ofreceiving two battery packs and the duct of FIG. 9 that forms a portionof the venting system. Certain parts of the battery charger and ventingsystem are not shown to better illustrate the duct.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings and initially to FIG. 1, a prior artbattery cell is shown. The prior art battery cell 1 has a cylindricalcase that contains the cell materials in a closed fashion by a cover 11.A conductive projection 11 a is formed in the cover 11, and a safetyvalve for releasing gasses is disposed in the projection 11 a.Generally, the cover 11 having the projection 11 a is the positiveelectrode and the case 12 is the negative electrode. Generally, an outersleeve 13 is formed from an electrically insulating material so thatwhen the battery cells are intentionally or unintentionally touchingeach other at the peripheral side face, the battery cells will notdischarge.

When the prior art cylindrical cell 1 is to be used as a power sourcefor an apparatus, generally, a plurality of cells are connected to eachother to form a cell pack, as shown in FIG. 2. Two adjacent cells 1 arebridged by an electrically conductive plate 9, such as a nickel plate.The plate 9 may be attached by spot-welding or other method of attachingthe plate 9 to the projection 11 a of the cover 11 of one of the cellsand the bottom face of the case 12 of the other cell, respectively. Thesleeve 13 acts to prevent adjacent cells from shunting. In thedescription of the embodiments of the present invention, componentshaving the same function as those of the prior art described above withrespect to FIG. 1 and 2 are designated by the same reference numerals.

Turning now to FIG. 3, one embodiment of the present invention is shown.Although the cell 1 is depicted with a cylindrical shape, it is to beunderstood that the cell 1 can have any suitable shape presently knownor that can be contemplated in the future. In general, the cell 1 has afirst end 2 end and a second end 3 spaced from the first end 2 to definea peripheral side face 4 that extends from the first end 2 to the secondend 3. A longitudinal axis 5 extends from the first end 2 to the secondend 3 of the cell 1. The first end 2 has a cover 11 from which aprojection 11 a extends. The projection 11 a defines a positiveelectrode or terminal. The second end 3 defines a negative electrode orterminal. While the cell 1 may be a nickel-cadmium cell or anickel-metal hydride cell, the present invention is not restricted thosetypes of cells.

According to another embodiment of the present invention, the cell 1 isprovided with a sleeve 30 that surrounds the peripheral side face 4 ofthe cell 1. The sleeve 30 made be made of any suitable electricallyinsulating material. For example, the sleeve 30 may be made from paper,plastic, or any other suitable insulating materials. The sleeve 30 maybe a molded plastic mesh or similar construction.

Desirably, the sleeve 30 is provided with a plurality of apertures 32 toallow heat to dissipate from the cell 1. The apertures 32 may have anysuitable shapes such that the cell 1 is sufficiently exposed to allowheat to dissipate while still allowing the cell 1 to be insulated whencontacted by a similar cell 1 having a sleeve 30. Suitable shapesinclude those selected from a circle, ellipse, parabolic, crescent,obround, disc, triangle, rectangular, polygonal, and mixtures thereof.Where the aperture 32 has a shape that provides a longer side (or a pairof longer sides) and a short side (or a pair of shorter sides, like anobround, the longer side(s) may be arranged to be parallel to thelongitudinal axis 5. Alternatively, the longer side(s) may be arrangedto be normal to the longitudinal axis 5.

To form a cell pack 20, a plurality of individual cells 1 areelectrically connected to each other. FIG. 3 shows the case where a cellpack is configured by six cylindrical cells 1. One skilled in the artwill understand that this embodiment of the present invention isapplicable to any number of battery cells and is applicable to any shapeof battery cell. Of course, in the case where two or more cells 1 areused, a cell pack 20 is configured by connecting the cells 1 to eachother by an electrically conductive connecting member 9. Instead ofconnecting the cells 1 in series, the cells 1 may be connected inparallel or in a combination of series and parallel connections.Accordingly, the connecting member 9 may connect adjacent positiveterminals, adjacent negative terminals, both, or adjacent positive andnegative terminals.

The electrically conductive connecting member 9 may be formed from anysuitable electrically conductive material. Non-limiting examples includenickel, nickel and steel composites, steel, or nonferrous conductivematerial. The electrically conductive connecting member 9 may beattached by spot welding or by any other suitable attachment method suchas laser welding.

Next, with reference to FIGS. 4 and 5, an embodiment of the carrier ofthe present invention in which fifteen cylindrical cells are held willbe described. In the present invention, however, the kind and shape ofthe cell 1 are not restricted to nickel-cadmium or nickel-metal hydrideand conventional manganese cells or sealed-type cells of other typessuch as those of rectangular cells may be used. In addition, while thepresent invention will be illustrated and described with fifteen cells,one skilled in the art will appreciate that the carrier will be suitablefor use with any number of cells, for example, twelve, ten, seven, four,or even two depending on the desired voltage output.

As shown in FIG. 4, the fifteen cells 1 are arranged in three rows witheach row consisting of five cells 1. The fifteen cells 1 are sandwichedbetween an upper carrier 40 and a lower carrier 50 to define a carrier60. Desirably, the upper carrier 40 and lower carrier 50 are made of anelectrically insulating material such as a synthetic resin. The uppercarrier 40 and the lower carrier 50 have a significant portion that issubstantially flat. The thickness of the upper carrier 40 and the lowercarrier 50 ranges from about 0.25 mm to about 25 mm, desirably fromabout 0.5 mm to about 10 mm, more desirably from about 0.75 mm to about1.25 mm. The upper carrier 40 and lower carrier 50 are used while beingdisposed opposing each other.

The upper carrier 40 has an upper surface 41 and a lower surface 42,which faces the battery cells 1. The upper carrier 40 has a plurality ofribs 43 extending outward from the lower surface 42. The ribs 43 arelocated on the upper carrier 40 in certain areas to cooperativelyinteract with and engage the battery cells 1 to correctly position themwith respect to each other. In this regard, the ribs 43 are spaced fromeach other and therefore they do not completely surround the cell 1.

The number of ribs 43 provided will be that necessary to selectivelyposition the number of cells 1 forming the desired cell pack 20. inaddition, when the upper carrier 40 is placed on the plurality ofbattery cells 1 the ribs 43 extend from upper carrier 40 a distancesubstantially less than the distance from the top 2 to the bottom 3 ofthe cell 1. Because the cell 1 may have any of a variety of differentshapes and heights, the length of the ribs 43 will vary depending on theshape of the cell 1. Desirably, the ribs 43 extend a distance less thanone-half the distance from the top 2 to the bottom 3 of the cell 1. Forexample, the ribs 43 extend from the lower surface 42 a distance rangingfrom about 0.5 mm to about 10 mm, desirably from about 3 mm to about 6mm.

The upper carrier 40 is provided with shaped cut-outs 44 thatsubstantially conform to the shape of the electrically conductiveconnecting member 9. Thus, when the connecting member 9 is rectangular,the cut-out 44 will likewise have a rectangular shape with dimensionssubstantially the same (slightly larger) as the dimensions of theconnecting member 9. The thickness of the upper carrier 40 may besubstantially the same as the thickness of the connecting member 9 sothat when the upper carrier 40 is placed on top of the plurality ofcells 1 forming the cell pack 20, the upper surface of the connectingmember 9 and the top surface 41 of the upper carrier 40 will lie insubstantially the same plane. Alternatively, the connecting member 9 canhave a thickness slightly less than the thickness of the upper carrier40 so that the connecting member 9 does not extend beyond the topsurface 41 of the upper carrier 40.

The upper carrier 40 is also provided with a plurality of vent openings46. In general, the vent openings 46 are provided on the upper carrier40 at a location that is aligned with a gap 6 formed by adjacent cells1. For example, referring to FIG. 4, a gap 6 is formed by three adjacentcells 1. By providing vent openings 46 on the upper carrier 40, fluidflowing through the gap 6 can also flow through the vent openings 46 tomore effectively dissipate heat generated by the cells 1.

The lower carrier 50 has a lower surface 51 and an upper surface 52,which faces the battery cells 1. The lower carrier 50 has a plurality ofribs 53 extending outward from the upper surface 52. The ribs 53 arelocated on the upper carrier 50 in certain areas to cooperativelyinteract with and engage the battery cells 1 to correctly position themwith respect to each other. In this regard, the ribs 43 are spaced fromeach other and therefore they do not completely surround the cell 1. Inaddition, the ribs 53 are also located in areas on the lower carrier 50so that when the upper carrier 40 and the lower carrier 50 are placed onthe cells 1 to effectively sandwich the cells 1, the cells 1 will bealigned substantially vertically and parallel to each other, i.e.,parallel to the longitudinal axis 5.

The number of ribs 53 provided will be that necessary to selectivelyposition the number of cells 1 forming the desired cell pack 20. Whenthe lower carrier 50 is placed on the plurality of battery cells 1 theribs 53 extend from lower carrier 40 a distance substantially less thanthe distance from the bottom 3 to the top 2 of the cell 1. Because thecell 1 may have any of a variety of different shapes and heights, thelength of the ribs 53 will vary depending on the shape of the cell 1.Desirably, the ribs 53 extend a distance less than one-half the distancefrom the bottom 3 to the top 2 of the cell 1. For example, the ribs 53extend from the upper surface 52 a distance ranging from about 0.5 mm toabout 10 mm, desirably from about 3 mm to about 6 mm.

The lower carrier 50 is provided with shaped cut-outs 54 thatsubstantially conform to the shape of the electrically conductiveconnecting member 9. Thus, when the connecting member 9 is rectangular,the cut-out 54 will likewise have a rectangular shape with dimensionssubstantially the same (slightly larger) as the dimensions of theconnecting member 9. The thickness of the lower carrier 50 may besubstantially the same as the thickness of the connecting member 9 sothat when the lower carrier 50 is placed on the plurality of cells 1forming the cell pack 20, the exposed surface of the connecting member 9and the lower surface 51 of the lower carrier 50 will lie insubstantially the same plane. Alternatively, the connecting member 9 canhave a thickness slightly less than the thickness of the lower carrier50 so that the connecting member 9 does not extend beyond the lowersurface 51 of the lower carrier 50.

The lower carrier 50 is also provided with a plurality of vent openings56. In general, the vent openings 56 are provided on the lower carrier50 at a location that is aligned with a gap 6 formed by adjacent cells1. For example, referring to FIG. 4, a gap 6 is formed by three adjacentcells 1. In addition, the vent openings 56 provided on the lower carrier50 are aligned with the vent openings 46 provided on the upper carrier40. By aligning the vent openings 46, 56 and the gap 6, fluid flowingthrough the gap 6 can also flow through the vent openings 46, 56 to moreeffectively dissipate heat generated by the cells 1.

As shown in FIG. 5, the carrier 60 causes the cells 1 to be positionedin such a manner that the end portions 2 and 3 are in the substantiallysame plane. In this case, the electrically conductive connecting member9 is not required to be bent and can be made flat so that the terminalsare easily connected to each other.

In addition, In the cell pack shown in FIG. 5, in which the cylindricalcells 1 are held by the carrier 60, as described above, ventilation isenabled between the exterior and the vicinity of the inward-directedperipheral side faces of the cylindrical cells 1, via the vent openings46, 56 provided in the upper carrier 40 and lower carrier 50,respectively, which as noted above are longitudinally aligned.Consequently, heat generated from the cylindrical cells 1 can be rapidlydissipated to the exterior and the temperature rise of the cylindricalcells 1 is reduced so that it does not exceed the specified range.

It is believed that the cells 1 closest to the center of the cell pack20 tend to cool slower than those cells farthest from the center of thepack. Therefore, the size of the vent openings 46, 56 can be varied sothat the vent openings 46, 56 closest to the center of the cell pack 20are larger than the vent openings farthest from the center of the cellpack 20.

The ventilation due to the vent openings 46, 56 and the like can occuras a result of natural convection. When the amount of generated heat isexpected to be large or is large, the natural convection can be enhancedby providing a fluid moving device to force a fluid around the outwarddirected peripheral side face 4 of the cells 1 and through the ventopenings 46, 56 provided in the upper carrier 40 and lower carrier 50.

The carrier 60 of the present invention may be used with cells 1 thatare bare or do not have any insulating cover. In this instance, the ribs43, 53 are located on the upper carrier 40 and lower carrier 50,respectively so that adjacent cells 1 do not touch. As a result,effective heat dissipation can occur. Alternatively, the carrier 60 ofthe present invention may be used with cells 1 that are provided withsleeves 30 according to the present invention or with standard knowncells.

A filter (not shown) may be placed adjacent each of the upper carrier 40and lower carrier 50 to reduce or prevent dust entering the cell pack20. The filter may be any suitable material such as a synthetic fibermesh.

The cell pack may also have a temperature indicating device to indicatethe temperature of one or more cells 1 in the cell pack 20. Thetemperature indicating device may be thermistor, a capacitor, atheromostat, or other temperature indicating device.

One skilled in the art will understand that the cell pack of the presentinvention can be provided with one or more electrical contacts thatoperatively associated with the cell pack 20. The electrical contactsact as a conduit of electricity from the cell pack 20 to the motor of apower tool with which the cell pack 20 is associated. In addition, theelectrical contacts act to transfer the charge from a charger so thatthe cells in the cell pack 20 can be recharged.

In addition, it is customary to provide a housing 100 that surrounds thecells 1 and cell pack 20 to define a battery pack 102. In this regard,FIG. 6 shows a battery charger 200 incorporating a venting system 220and having two battery packs 102 operatively associated with the charger200. The housing 100 may be formed from any suitable material but istypically formed of a hard plastic to aid in protecting the cells. Theupper 110 and lower 120 faces of the battery pack 102 may contain vents112, 122 to allow fluid to pass through the housing 100 and the vents46, 56 provided on the upper carrier 40 and the lower carrier 50.Although it is understood that the upper 110 and lower 120 faces of thebattery pack 102 are relative, for ease of description, the upper face110 of the battery pack 102 will be considered to be that face adjacentthe upper carrier 40 and the lower face 120 of the battery pack 102 willbe considered to be that face adjacent the lower carrier 50. The batterypack 102 may be slideably engaged with a power tool such that thebattery pack 102 can be removed from the power tool and placed in acharger 200 for recharging the cells 1.

The charger 200 includes a housing having one surface that receives abattery pack. For convenience the charger 200 will be described ashaving a top 202, a bottom 204, and at least one side 208. It will beunderstood, however, that the configuration of the charger 200 is notparticularly important so long as the features described below areincorporated. In addition, for convenience, the one surface will bereferred to as the top surface 202. The top surface 202 is provided withat least one slot 210 to removably receive a battery pack. In a desiredembodiment, the charger 200 is provided with two slots 210 a, 210 b tosimultaneously receive two separate battery packs 102. Each slot 210 hasrespective contacts to couple with the electrical contacts 70 associatedwith the cell pack 20 to charge the cells 1. The charging of the cells 1may be controlled by a switch, a microcontroller, a circuit or the like.Methods of designing and operating the charging mechanism are known andany of several different operating schemes may be used.

The charger 200 further includes a venting system 220 that includes aninlet 222, an outlet 224, a fan 226, and a duct 230 to direct fluid fromthe fan 226 to the outlet 224. The outlet 224 is associated with vents122 provided on the lower face 120 of the battery housing 100 so thatfluid flows from the fan 226, through the duct 230, into the batteryhousing 100 and through the vents 56 in the lower carrier 50, across thecells 1 and out the vents 46 in the upper carrier 40 and the vents 112in the upper face 110 of the battery housing 100. Alternatively, the fan226 may be arranged to suck fluid from the outlet 224 to the inlet 222so that the fluid is moved from the vents 112 on the battery housing 100through the vents 46 in the upper carrier 40, across the cells 1 throughthe vents 56 in the lower carrier 50 and into the duct 230. It will beunderstood by one skilled in the art the terms inlet and outlet arerelative to the direction of the fan flow. For ease description, the fanflow will be described as moving fluid from the charger housing 200 intothe battery housing 100. Accordingly, the outlet 224 of the chargerhousing 200 will be disposed on the top 202 of the charger housing 200and will be associated with the vents 122 provided on the lower face 120of the battery housing 100.

As noted above, the venting system 220 includes an inlet 222 that may beprovided on the top 202 of the charger housing 200, the bottom 206 ofthe charger housing 200, the side(s) 208 of the charger housing 200 oreach of them. The inlet 222 may be provided by a grill, slots, or othertypes of openings such that fluid, typically air, can pass into thecharger housing 200 to the fan 226. A filter may be provided adjacentthe inlet to reduce or prevent particles such as dust from entering thecharger housing 200.

The outlet 224 is provided on the top 202 of the charger housing 200such that when a battery pack 102 is positioned on the charger 200, theoutlet 224 is aligned with the vents 122 provided on lower face 120 ofthe battery pack 102 so that fluid may enter the battery pack 102. Forexample, the top 202 of the charger 200 has a slot 210 to receive thebattery pack 102. The outlet 224 may be provided within the confines ofthe slot 210 or adjacent to the slot 210 so long as the outlet 224 isadjacent the vents 122 provided on the lower face 120 of the batterypack 102.

In the desired embodiment, the charger 200 is provided with two slots210 a and 210 b so that two battery packs 102 may be simultaneouslylocated on the charger 200. In this instance, at least one outlet 224 aand 224 b will be respectively associated with each slot 210 a and 210b. A screen or grill may be located adjacent the outlet 224 to reduce orprevent dust, chips, or other things from entering the battery pack 102.

A duct 230 fluidically connects the fan 226 to the outlet 224. The duct230 has a bottom wall 232 with a side wall 234 extending from theperiphery of the bottom wall 232. The bottom wall 232 is provided with acentral portion 236 having a first arm 240 and a second arm 244connected with and extending from the central portion 236. The duct 230is desirably formed with smooth contours to minimize flow and pressuregradients. The bottom 232 may be T-shaped, Y-shaped, or shaped in asimilar fashion such that fluid can flow from a central portion 236 tothe first 240 and second 244 arms. The bottom wall 232 has an aperture238 to receive the fan 226. Desirably, the aperture 238 is provided inthe central portion 236 so that fluid is distributed about equally toeach of the first arm 240 and second arm 244 of the duct 230.

The first arm 240 terminates at a terminal end 242 and the second arm244 terminates at a terminal end 246 with the terminal ends 242, 246located adjacent respective outlets 224 a, 224 b. A seal may be providedbetween the terminal end of the arms 242, 246 and the outlet 224 toreduce or prevent fluid from by passing the outlet 224.

The duct 230 is desirably located within the charger housing 200 suchthat the underside 204 of the top 202 of the charger housing 200 forms atop surface of the duct 230. In this way, the duct 230 will be closedexcept for the portion that is adjacent to the outlet 224.Alternatively, the duct 230 can be provided with a top housing (notshown) to enclose the side wall 234 except at the terminal end of thearms 242, 246. It will be appreciated that when the fan 226 isactivated, fluid is directed from the fan inlet, into the duct 236 andthrough the terminal ends of the arms 242, 246 to the respective outlet224 a, 224 b and through the vents 122 on the lower face 120 of thebattery housing 100.

The fan 226 can be activated as desired. For example, the chargerelectronics could be coupled with a sensor inside the battery pack 102that would be activated through the electrical contacts. The sensorcould sense a property of the cell pack 20 such as voltage of one ormore cells 1, temperature within the cell pack 20, or other property.Based on the output of the sensor, the fan 226 could be activated torun. Alternatively, the fan 226 could be activated to continuously beactivated while the charger is operating. The fan 226 could also beactivated through the use of a manual switch provided on the chargerhousing 200.

In yet another alternative, a mechanical switch may be provided suchthat when a battery pack 102 is positioned within a slot 210 of thecharger housing 200, the fan 226 can be activated. In this embodiment,when the battery pack 102 is removed from the slot 210, the fan 226 willbe de-energized.

Other fan modulation process may also be used. For example, the fan 226may be turned on for a predetermined period and turned off before abattery pack 102 is disposed on the charger 200. This period could occurwhen the charger 300 is either turned on, connected to an electricaloutlet or when a button on the charger 200 is pushed. This would blowforeign particles, such as dust, that has settled on the charger 200 andor the slot 210. Accordingly, the particles or dust would not be blowninto the battery pack 102 during charging. This result can also beachieved if the fan 226 is always on, on after the battery pack 102 hasbeen removed, or if the fan 226 is periodically turned on and off whenthe battery pack 226 is not disposed in the charger 200.

In addition, rather than fan 226 being completely turned off, it may beexpedient to just regulate the power sent to the fan 226 so that the fan226 rotates at a lower speed. Accordingly, the fan 226 can rotate at afirst speed before the battery pack 102 is disposed on the charger 200.When the battery pack 102 is disposed on the charger 200, the fan 226can rotate at a second speed, which is higher than the first speed. Whenthe battery pack 102 is removed, the fan 226 can be turned offcompletely or brought back to a lower speed. This would also help inmaintaining the duct 230 free of dust.

It may be desirable to turn the fan 226 on at a high first speed for apredetermined period and then lower the speed before a battery pack 102is disposed on the charger 200. This period could occur when the charger200 is either turned on, connected to an electrical outlet or when abutton on the charger 200 is pushed.

Furthermore, the charger 200 can control the speed of the fan 226 byusing information from the temperature indicating device. For example,the charger 200 would receive information from the temperatureindicating device. If the battery pack 102 is below a first desiredtemperature, the charger 200 would lower the speed or stop the fan 226.Similarly, the charger 200 can control the fan 226 to maintain thetemperature of battery pack 102 near a predetermined temperature.

In addition, the charger 200 can control the fan 226 to obtain accurateinformation from the temperature indicating device. For example, if thetemperature indicating device was exposed to the air or fluid flow, thetemperature indicating device might indicate a cell temperature lowerthan the actual cell temperature. Such result can be minimized oravoided if the charger 200 periodically lowers the speed of or stops thefan 226 for a predetermined period of time. This would allow thetemperature indicating device to indicate or show a more accurate celltemperature, which can then be read by the charger 200 and used in itstemperature analysis. The charger 200 can then increase the speed of orstart the fan 226 until the next time the charger 200 needs temperatureinformation.

While the invention has been described in conjunction with specificembodiments it is to be understood that many alternatives,modifications, and variations will be apparent to those skilled in theart in light of the foregoing detailed description. It is thereforeintended that the foregoing description be regarded as illustrativerather than limiting, and that it be understood that it is the followingclaims, including all equivalents, that are intended to define thespirit and scope of this invention.

1-22. (canceled)
 23. A battery venting system comprising: a. a chargerincluding a first surface for electrically coupling with at least twochargeable battery packs; b. a first outlet provided on the firstsurface and located adjacent at least a portion of a vent system of abattery pack; c. a second outlet provided on the first surface andlocated adjacent at least a portion of a vent system of another batterypack; d. a mechanism in the charger for simultaneously moving fluidthrough the vent system of the at least two battery packs.
 24. Thebattery venting system of claim 23 wherein the mechanism in the chargerincludes a fan.
 25. The battery venting system of claim 24 wherein themechanism in the charger includes a duct to fluidically connect anoutput of the fan with each of the outlets.
 26. The battery ventingsystem of claim 25 wherein the duct includes a central portion with afirst arm and a second arm extending from the central portion.
 27. Thebattery venting system of claim 26 wherein the duct is substantiallyT-shaped.
 28. The battery venting system of claim 24 wherein the fan ismodulated by a sensor.
 29. The battery venting system of claim 23wherein the housing is removably coupled with a cordless power tool. 30.The battery venting system of claim 23 wherein the charger sequentiallycharges the at least two chargeable battery packs.
 31. The batteryventing system of claim 23 wherein the charger simultaneously chargesthe at least two chargeable battery packs.
 32. A battery chargercomprising: a. a charger including a first surface for electricallycoupling with at least two chargeable battery packs, wherein the chargersimultaneously charges the at least two chargeable battery packs; and,b. a mechanism associated with the charger for simultaneously movingfluid through a vent system of the at least two battery packs.
 33. Thebattery charger of claim 32 further comprising a first outlet providedon the first surface and located adjacent at least a portion of the ventsystem of a respective one of the at least two battery packs.
 34. Thebattery charger of claim 33 further comprising a second outlet providedon the first surface and located adjacent at least a portion of the ventsystem of a respective another one of the at least two battery packs.35. A battery charger comprising a charger including a first surface forelectrically coupling with at least two rechargeable battery packs,wherein the charger simultaneously charges the at least two rechargeablebattery packs.
 36. The battery charger of claim 35 wherein the firstsurface slidably receives the at least two rechargeable battery packs.37. The battery charger of claim 35 wherein the first surface includesat least two slots to respectively receive the at least two rechargeablebattery packs.
 38. The battery charger of claim 37 wherein the at leasttwo slots include electrical contacts.
 39. The battery charger of claim28 wherein the sensor senses one of a voltage of at least one cell ofthe battery pack or a temperature within the battery pack.
 40. Thebattery charger of claim 28 wherein the sensor senses a temperaturewithin the charger.
 41. The battery charger of claim 34 furthercomprising an inlet to the mechanism wherein fluid flows from the inletthrough the vent system of the at least two battery packs.
 42. Thebattery charger of claim 41 further comprising a sensor to control themechanism.